1. Field of the Invention
The present invention relates to a toner cartridge replaceably attached to an electrophotographic image forming apparatus, and to an image forming apparatus including the same.
2. Description of the Related Art
Conventionally, electrophotographic image forming apparatuses such as copiers, printers, and facsimile machines, which use dual-component developers, are each capable of continuously driving to output images by being automatically supplied with a toner from a toner discharge port of a toner cartridge replaceably attached to an apparatus body to a developing section of the apparatus.
As shown in FIG. 10, what has been proposed as such a toner cartridge 300 is the one including: a toner cartridge body 301 having a toner discharge port 304a; a shutter 303 provided on the outer surface side of the toner cartridge body 301 for opening and closing the toner discharge port 304a; an auger screw 302 rotatably provided in the toner cartridge body 301 for conveying a toner T in the toner cartridge body 301 to the toner discharge port 304a; and a paddle member 306 rotatably provided in the toner cartridge body 301 so as to be in parallel to a rotary shaft 302a of the auger screw 302 for sending the toner T in the toner cartridge body 301 toward the auger screw 302, in which the toner discharge port 304a is disposed on one end side in a longitudinal direction of the toner cartridge body 301.
As a device that resembles the toner cartridge shown in FIG. 10, what has been proposed is the one disclosed in Japanese Unexamined Patent Publication No. 2000-214667, for example.
In a case where the toner cartridge 300 shown in FIG. 10 is stored upright with the toner discharge port 304a facing downward, the toner T in the toner cartridge body 301 sinks down under its own weight over the course of time, and hence a toner density around the toner discharge port 304a becomes high. As a result, there arises a problem that the toner T around the toner discharge port 304a flocculates, and eventually forms lumps, to clog the toner discharge port 304a. It is to be noted that any part in FIG. 10 where black dots appear densely represents such a flocculated toner T or a lump of the toner T.
While the manufacturers recommend users not to store the toner cartridge 300 in such an upright state, in some cases, this is not complied with.
Depending on vibrations or load conditions of the toner cartridge 300 during transportation, the toner density around the toner discharge port 304a may become high to result in the flocculation.
In a case where the toner cartridge 300 whose toner discharge port 304a is clogged with such a flocculated toner T or lumps of the toner T is attached to the apparatus body of the image forming apparatus, the toner T is not easily discharged from the toner cartridge 300. This may cause the apparatus body to determine that the toner has run out, even when a large amount of the toner T remains in the toner cartridge 300.
Further, the flocculated toner T or lumps of the toner T around the toner discharge port 304a may be compressed and thus solidifies under the pressure of the auger screw 302, resulting in a failure of the auger screw 302 being locked.
Accordingly, as to an attachment of a new toner cartridge to the apparatus body, the manufacturers recommend the users to follow a precaution of shaking the toner cartridge for several times before attaching it. However, in some cases, this is not complied with.
Further, because a recently toner has its fusing performance under low temperatures improved for the energy-saving purpose, its storage stability is reduced, and hence such a toner is prone to the toner flocculation when left at an ambient temperature.
Still further, in accordance with the miniaturization demanded for recently image forming apparatuses, the toner cartridge also is subjected to miniaturization, and hence the toner cartridge body is tightly packed with the toner. Therefore, the toner flocculation is prone to occur.
The toner cartridge disclosed in Japanese Unexamined Patent Publication No. 2000-214667 is directed to prevent the toner flocculation by partially cutting a helical blade of the auger screw on the toner discharge port side, so as to reduce the pressure applied by the auger screw to the toner on the toner discharge port side when the toner is conveyed. However, this cannot address the toner flocculation that occurs when the toner cartridge is stored upright with the toner discharge port facing downward.